B cell multiple sclerosis (MS) research has focused on antibody (Ab)-dependent B cell functions, since a definite hallmark of MS is an elevated intrathecal Ab production. The advent of Rituximab has shown that B cells play a role as antigen presenting cells in MS. This B cell depleting Ab reduced the T cell number as well as MS lesions, but did not alter Ab levels. Little research has studied the capability of B cells to participate in MS pathogenesis by antigen presentation. We hypothesized that the antigen presentation capacity of B cells is increased in MS. Indeed, the expression of peripheral CD80+ and intrathecal CD86+ B cells was increased in MS patients compared to healthy persons (HC). Moreover, CD80+ B cells were detected in MS brains, while no infiltrates were found in healthy brains. These findings suggest that costimulatory molecules increase the antigen presentation capacity of B cells in MS.
In addition, MS patients showed B cell reactivity in response to myelin and vi